The present invention has its origin in the need to wipe away water, dirt or the like from a windscreen on a vehicle. In an active operating position, an arrangement suited for the purpose should wipe as large a part of the windscreen as possible, and in an inactive resting position it should intrude as little as possible on the windscreen and into the field of vision of the operator of the vehicle.
A generally adopted way of attempting to meet the abovementioned need is to let a wiper blade carry out a pivoting movement across the windscreen. For this purpose, the wiper blade is suitably arranged centrally on the lower edge of the windscreen or centrally on the upper edge of the windscreen in such way that it can pivot. On account of the positioning and the design described, only a limited arc-shaped segment of the windscreen is wiped. The disadvantages of this type of design can be solved to a certain extent. One way is to use two wiper blades of the type described above, which are placed in such way that they can carry out a pivoting movement over separate areas of the windscreen. Another way is to let a single centrally arranged wiper blade also move radially forward and back relative to the point of attachment to the vehicle, during a pivoting movement. That is to say that in a radial direction the wiper blade follows, for example, a cam curve that partially corresponds to the shape of the windscreen. However, none of these solutions fulfills the abovementioned need in a satisfactory way. A large part of the windscreen remains unwiped by the wiper blade or blades.
A design which better fulfills the basic need comprises a wiper blade that is connected to two arms. The arms are arranged centrally at the lower edge of the windscreen or centrally at the upper edge of the windscreen. In addition, the arms are preferably parallel and pivot in a synchronized way. The design means that, during the whole pivoting sequence, the wiper blade moves parallel in a transverse direction to its main extent and in an arc across the windscreen. However, even with this design, there is still the disadvantage that a large part of the windscreen remains unwiped.
U.S. Pat. No. 6,065,179 shows an arrangement that is based partially upon the abovementioned concept. The document shows a wiper blade that moves parallel throughout the whole wiping sequence, with the wiper blade being almost as long as one of the dimensions of the windscreen and with the wiper blade being moved forward and back across the windscreen transverse to the direction of the main extent of the wiper blade. As a result of this design, more or less the whole windscreen is wiped. A disadvantage of the arrangement that is described in the document U.S. Pat. No. 6,065,179 is, however, that the arrangement takes up space outside and around the windscreen that is to be wiped. An additional disadvantage is that the wiper blade in the document rotates somewhat. The rotation means that the wiper blade does not move completely parallel throughout the whole wiping sequence. In addition, the wiper blade moves vertically up and down, which is not favorable as far as efficiency in wiping is concerned.
Modern working machines and similar vehicles are equipped with large windscreens which almost completely take up the whole front of the cab. The vehicles have also large side windows and roof windows which more or less merge into the windscreen, which means that the windscreen wiper must be more compact than the one shown in U.S. Pat. No. 6,065,179. A compact windscreen wiper means that it can be positioned in such a way that it does not intrude on the field of vision of the operator of the vehicle.